Is the ceiling space used for an environmental air return and is this commercial or residential? Have you determined if this is a plenum or environmental air handling space? If it isn't then there is no requirement for plenum rated materials or wiring methods.
In general most armored cable can be used in a plenum environment. Check the manufacturer. There are, of course, plenum listed versions of FO cables and many types of coax that can be installed directly.
Non-plenum listed cables can be installed in a plenum space only if pulled through conduit, if that is what you are asking.
-Hal
